To propel a bicycle, a user sits on a seat and straddles a frame with his or her legs. A pair of pedals are connected to each other with a pair of crank arms that are connected to a gear assembly. The pedals are positioned to be engaged by the feet and to travel in a reciprocating motion powered by the user's feet. The gear assembly directs the energy exerted through the user's feet to an axle of one of the wheels of the bicycle, which causes the wheel to turn. Such rotation of the wheel propels the bicycle forward. The speed at which the bicycle travels is dependent on the amount of resistance on the bicycle and the amount of energy that the user exerts with his or her legs to rotate the wheel. The resistance on the bicycle generally includes the collective weight of the bicycle and the user as well as the slope of the terrain on which the bicycle is being propelled. In the case of a stationary bicycle, the resistance may be provided with a magnetic resistance mechanism, a pneumatic resistance mechanism, a hydraulic resistance mechanism, a gear type resistance mechanism, braking pads, tensioning elements, fan blades, another type of resistance mechanism, or combinations thereof.
One mechanism for measuring the amount of energy exerted by the user is disclosed in U.S. Patent Publication No. 2003/0074985 issued to Gordon Liao. In this reference, a sensor of the pedaling force of a power-assisting bike includes a transmission system provided with at least one pair of screw gears. One of the screw gears is activated by the pedaling force to rotate at an original location and the other driven by a screw gear engaging to rotate and shift along a shaft, with a resilience member fitted at an end side. An annular magnet is fitted around the end of the shaft of the resilience member and the screw gear, capable to shift together with the screw gear. A Hall sensor is provided on a fixed side of the annular magnet. Thus, the lateral force produced by the screw gears can detect an axially shifting distance of the screw gear and give out a voltage signal to control a motor to output motive power for the bike. Another type of mechanism for measuring the amount of energy exerted by the user is described in U.S. Pat. No. 8,011,242 issued to George David O'Neill. Each of these references are herein incorporated by reference for all that they disclose.